High vacuum still



March 7, 1944. K. c. D. HICKMAN HIGH VACUUM STILL KNETH CDHICKZWININVENTOR BY z ATTORNEYS Filed March 4, 1942 problem to solve.

Patented Mar. 7, 1944 HIGH VACUUM STILL Kenneth C. D. Hickman,Rochester, N. Y., as-

signor to Distillation Products, Inc., Rochester, N. Y., a corporationof Delaware Application March 4, 1942, Serial No. 433,337

10 Claims.

This invention relates to improved high vacuum stills and particularlyto improved high vacuum stills in which the distilland is distributedover the vaporizing surface by centrifugal force and the distillingvapors are condensed upon a rotating condensing surface.

In my Patent 2,210,928, August 13, 1940, I have described high vacuumunobstructed path centrifugal stills in which the distilland isintroduced on to a rotating vaporizing surface and condensate iscondensed upon a rotating condensing surface, the condensing surfacebeing adapted to throw the liquid condensate by centrifugal force into agutter arranged at the periphery of the condensing surface. Also, inHickman and Hecker Patent 2,180,052, November 14, 1939, there isdescribed similar stills provided with rotating condensing surfaceshaving slots to permit the escape of non-condensable gas. Cooling of therotating condensing surface .has been a difficult Introduction ofdistilland on to the condensing surface results in intermixture ofcondensate and distillate. Cooling by radiation from an adjacent coolingsurface is frequently insufficient.

This invention has for its object to provide simple and economical meansfor efficiently cooling a rotating condensing surface of a centrifugalstill. Another object is to make available a high vacuum unobstructedpath still provided with a condensing surface which has slots soarranged that residual gas can pass through the condensing surface intothe evacuating pumps, and which are also arranged so that rotation ofthe slotted condensing surface results in partial evacuation of thestill. lA still further object is to provide a high vacuum unobstructedpath still having a rotating condensing surface which is slotted, theslots being so arranged that condensate and cooling fluid introducedthereon is transferred to the opposite side of the condensing surfacefrom thevaporizing surface. Other objects will appear hereinafter.

These and other objects are accomplished by my invention which includesa high vacuum unobstructed path still having a rotating condensingsurface and slots thereon so arranged that the condensate is thrown tothe rear of the surface thence travels to an adjacent cool surface orcooler and the cooled liquid condensate introduced back on to theslotted rotating condensing surface. I have also found that the slots orvanes of the rotating condensing surface can beso positioned or arrangedthat during rotation evacuation of the distilling space takes place. Myinvention, therefore, includes stills provided with rotating condensingsurfaces of this type.

In the following description I have given several of the preferredembodiments of my invention, but it is to be understood that these areset forth for the purpose of illustration and not in limitation thereof.

In the accompanying drawing I have illustrated two of the preferredembodiments of my invention wherein like numbers refer to like parts andwherein:

Fig. 1 is a vertical section of a centrifugal still having a rotatingcondensing surface and slots or vanes which are adapted to transfer theliquid thereon to the side of the condensing surface farthest from thevaporizing surface and which are adapted to evacuate the space betweenthe vaporizing and condensing surfaces; and

Fig. 2 is a vertical section of a modification of the apparatus shown inFig. 1, the condensing surface being bell-shaped to increase theeffective condensing area; and

Fig. 3 is a horizontal section of the rotating condensing surface takenon line 33 of Fig. 2.

Referring to Fig. 1, numeral 4 designates a cylindrical still casingprovided with a bellshaped base plate 6 integral therewith" and abellshaped removable cover 8. Numeral l0 designates a shaft rigidlymounted in a gas tight bear-' ing l2 which shaft is provided at one endwith a pulley l4 and at the other end with a flange l6. To the flange isrigidly mounted a circular vaporizing plate I8. The periphery of platel8 extends into an annular gutter 20 to which is connected withdrawalconduit 22. Numeral 24 designates an electrical heating resistance unitadapted to heat plate l8 to distilling temperature Numeral 26 designatesa conduit for introducing distilland on to the approximate center ofplate Numeral 28 designates a shaft rigidly held in a rotatable mannerby gas tight packed bearing 30. The upper end of shaft 28 is providedwith a driv ing pulley 32 and the opposite end of the shaft is integralwith circular condensing surface 34. The condensing surface isconstructed from a plurality of radical vanes which overlap in the samefashion as the blades of a windmill. The blades are spaced so as toallow passage of residual gas. The periphery of the condensing surface34 extends in'to annular gutter 36 to which is connected withdrawalconduit 38. Numeral 40 designates a cooler and reservoir through whichliquid from conduit 38 passes. Cooling takes place by introduction ofcooling liquid into the cooling Jacket It is also desirable, but notnecessary,

through conduit 42 and withdrawal through conduit 44. Numeral 46designates a conduit serving to convey liquid from cooler 40 to pump 46.Numeral 50 designates a conduit for conveying liquid from the exhaustside of pump 48 tothe approximate center of condensing surface 34.Numeral 52 designates a conduit provided with a valve 54 for withdrawingor bleeding off distillate from the system. Numeral 56 designatesconduits connected to evacuating backing pumps (not shown).

Referring to Fig. 2 numeral 60 designates a bellshaped still casingprovided with a gas tight base 62 which can be removed when the still isdisassembled. Numeral 62 designates a condensing surface constructed ofa number of radial vanes which overlap as illustrated in Fig. 3. Thevanes are assembled to form a unitary condensing surface having the bellshape illustrated. The base of each vane is provided with an outwardlyturned edge 64 which protrudes into gutter 66.

During operation of the apparatus illustrated in Fig. 1 the still isevacuated by means of backing pumps connected to conduits 56. Heatingresistance units 24 are put into operation and distilland is-introducedon to the center of the vaporizing plate l8 by way of conduit 26. Poweris applied to pulleys l4 and 32 to rotate the vaporizing and condensingsurfaces. Condensing surface 34 is rotated in the direction indicated bythe arrow. Distilland is caused to flow by centrifugal force over thesurface of plate I8 as a thin film. Vapors are efficiently formed andpass to the ccndensingsurface 34. Here they impinge upon the vanes dueto the fact that they overlap. They are then condensed and due to thecentrifugal action travel to the upper edge of each vane. In thisposition they cannot undesirably affect the thermal characteristics ofthe still. The condensate is then flung by centrifugal force into gutter36. Liquid condensate then flows through conduit 38 into cooler 40 andis pumped by pump 46 through conduit 50 back on to the condensingsurface 34. The liquid is then flung by centrifugal force over thevarious vanes of condensing surface 34 and is again recirculated throughpump 48 and conduit 50. When suflicient distillate has accumulated incooler 40 it is continuously or intermittently bled from the systemthrough conduit 52 and valve 54. Undi'stilled residue is removed fromthe collecting gutter by way of conduit 22. Gases in the distillingspace are continuously removed by the rotating vanes and are caused topass into conduits 56 from. which they are removed by the backing pumps.

It has been found that organic liquids distilled in high vacuum stillsare efficient absorbers and radiators of heat. For this reason it isdesirable to maintain the liquid, both on the vaporizing and condensingsurfaces, in a thin film. The construction shown in Fig. 1 performs thisdesirable function very efficiently. Both the initial condensate and therecirculated condensate are maintained on the upper edge of thecondensing vanes where they cannot absorb heat from the vaporizingsurface while condensate on the portions nearest the vaporizing surfaceis in such a thin film that it will not absorb heat. Th s isparticularly advantageous when the liquids are introduced on to thecondensing surface. Otherwise the cooling liquid would greatly increasethe thickness of the condensate film on the condensing surface. henceincreasing heat losses greatly. to maintain the vaporizing andcondensing surfaces in a highly polished condition. Highly polishedsurfaces in conjunction with thin films of condensate or distillandgreatly decrease the heat losses which are otherwise considerable inhigh vacuum unobstructed path stills.

In operating the apparatus illustrated in Figs. 2 and 3 the still isevacuated and the vaporizing surface is put into operation as describedin connection with Fig. 1. Condensing dome 62 is rotatedcounterclockwise. Condensate collecting on condensing dome 62 is atleast partially flung through the spaces between the vanes on to theoutside dome 60 which is air cooled. The condensate then partially dropsfrom the upper part and especially the top part of dome 60, after be ingcooled, back on to the vanes and hence cools them to an efficientcondensing temperature. The condensate eventually flows by gravity intogutter 66, but it may be transferred back and forth between thecondensing surface 62 and cool dome 60 many times before eventuallyreaching gutter 66. The condensate is then withdrawn from the systemthrough conduit 38. Parts of this withdrawn condensate may be cooled in40 and recycled back to 62 by way of conduit as described in connectionwith Fig. 1. This is advantageous when the shape of 62 and does notresult in suificient return of cooled condensate to condenser 62. Inaddition to the other advantages mentioned this particular constructionincreases the condensing area, and the effective pumping capacity of thevanes.

High vacuum unobstructed path distillation involves distillation atpressures of below approximatel 1 mm. and especially at pressures below.1 mm. suchv as .001 mm. A single backin pump cannot efficiently producesuch low pressures. Also at these low pressures gases diffuse and cannotbe sucked so that the removal of gases from the still depends upon theirrate of diffusion. The construction shown in Figs. 1 and 2 enablesimproved removal of the gases from the system and particularly from thespace between the vaporizing and condensing surfaces. Due to thepositioning of the vanes they tend to force the gases in the spacebetween the two surfaces toward the evacuating conduits 56 from whichthe gases can be more efficiently removed by the evacuating pumps. Thefaster the vanes rotate the better the pumping effect, Speeds of to10,0000 or more R. P. M. can be used but speeds of about 500 to 5,000will be found to be generally most useful.

Many modification can be made in the apparatus illustrated withoutdeparting from the spirit or scope of the invention. For instance, itwould be perfectly feasible to construct the apparatus of Fig. 1 so thatthe vaporizing and condensing surfaces are vertical. Some modificationwould be required to do this in connection with the apparatus of Fig. 2since return of the condensate to the condensing surface for coolingpurposes requires gravity flow. However, this apparatus could besimilarly modified by providing a circulating pump for the coolcondensate.

The invention described constitutes a simple and economical method forcooling slotted rotating condensing surfaces. The construction illustrated not only enables efllcient cooling, but at the same time permitsresidual gases to efliciently pass from the space between the condensingand vaporizing surfaces where they would otherwise harmfully affect thedistillation. A particular advantage of the invention is that the stillsare made to perform a. pumping action without any expenditure of energyin addition to that necessary to remove condensate. A further advantageis that the heat losses are reduced because of the transfer ofcondensate to the portion of the condensing surface farthest from thevaporizing surface and the maintenance of a very thin film ofcondensate, which does not absorb much heat. on the parts of thecondensin surface nearest the vaporizing surface.

What I claim is:

1. High vacuum distillation apparatus comprising a rotatable vaporizingsurface, a rotatable condensing surface separated from the vaporizingsurface by substantially unobstructed space, means for heating thevaporizing surface, a cooler for condensate positioned so that thecondensing surface is between said cooler and the vaporizing surface,slots in the condensing surfac so' positioned that during rotation ofthe condensing surface the condensate is transferred to the side of thecondensing surface opposite to the vaporizing surface and thence flungto the adjacent cating with that side of the condensing surface to whichthe gases are caused to pass, and means for removing condensate from thestill.

5. An evacuating high vacuum still comprising in combination arotatable, vaporizing surface, means for heating the vaporizing surface,means for introducing distilland on to the approximate center of thevaporizing surface, means for re-- cooler and means for returning atleast part of the cool condensate to the condensing surface.

2. High vacuum distillation apparatus com prising a. rotatable,substantially horizontal vaporizing surface, and a rotatable condensingsurface the axis of rotation of which is approximately at right anglesto the vaporizing surface,

the condensing surface being separated from the vaporizing surface bysubstantially unobstructed space, means for heating the vaporizingsurface, a cooler for condensate positioned so that condensate flungfrom the condensing surface during rotation thereof impinges upon thecooler, slots in the condensing surface so positioned that duringrotation thereof the condensate is transferred to the side of thecondensing surface opposite to the vaporizing surfac and thence flung tothe adjacent cooler, and means for returning at least part of the cooledcondensate to the condensing surface.

3. High vacuum distillation apparatus com-- prising an approximatelyhorizontal rotatable vaporizing surface, a be1l-shaped condensingsurface separated from the vaporizin surface by substantiallyunobstructed space the axis of rotation of the condensing surface beingapproximately at right angles to' the vaporizing surface,

a bell-shaped cooler at least partially surrounding the condensingsurface, slots in the condensthe condensing surface condensate is thrownto the side of the condensing surface away from provided with vane andslots therebetween said vanes bein so positioned that during rotationgases in the space between the vaporizing and condensing surfaces arecaused to pass to the side of the condensing surface farthest from thevaporizing surface, an evacuating port communimoving undistilled residuefrom the vaporizing surface, a rotatable condensing surface separatedfrom the vaporizing surface by substantially unobstructed space, saidcondensing surface being provided with vanes and openings therebetween,said vanes being positioned so that during rotation gases in the spacebetween the vaporizing and condensing surfaces are caused to pass to theside of the condensing surface farthest from the vaporizing surface, andso positioned that during rotation liquid condensate thereon istransferred to the portion of the vanes farthest from the vaporizingsurface, an evacuating port communicating with that side of saidcondensing surface to which the gases are caused to pass, and means forremoving condensate from the still.

6. An evacuating high vacuum still comprising in combination a rotatablevaporizing surface, means for heating the vaporizing surface, means forintroducing distilland on to the approximate center of the vaporizingsurface, means for removing undistilled residue from the vaporizingsurface, a rotatable condensing surface separated from the vaporizingsurface by substantially unobstructed space, said'rotatable condensingsurface being constructed of a plurality of overlapping radial vaneswith ample openings therebetween for passage of residual gas, and beingpositioned so as to pump gases when rotated, an

evacuating port communicating with that side of the condensing surfaceopposite from the vaporizing surface, and means for removing condensatefrom the still.

7. The apparatus defined in claim 6 in which must collide at least oncetherewith.

- ing surface so positioned that during rotation of 8. An evacuatinghigh vacuum still comprising in combination a rotatable vaporizingsurface, means for heating the vaporizing surface, means for introducingdistillandon to the approximate center of the vaporizing surface, meansfor removing undistilled residue from the vaporizing surface, arotatable condensing surface separated from the vaporizing surface bysubstantially unobstructed space, said condensing surface being providedwith vanes and openings therebetween said vanes being so positioned thatduring rotation gases in the space between the vaporizing and condensingsurfaces-are caused to pass to the side of the condensing-surfacefarthest from the vaporizing surface, means for collecting conmeans forreturning at least part of the cooled condensate to the vanes of thecondensing sur-- face, an evacuating port communicating with that sideof the condensing surface to which the gases are passed, and means forremoving at least part of the condensate from the still.

9. An evacuating high vacuum still comprising in combination a rotatablevaporizing surface, means for heating the vaporizing surface, mean! forintroducing distilland on to the approximate center of the vaporizingsurface, means for removing undistilled residue from the vaporizingsurface, a rotatable condensing surface separated from the vaporizingsurface by substantially unobstructed space, said condensing surfacebeing ing port communicating provided with vanes and openingstherebetween for the passage of residual gas, said vanes being sopositioned that during rotation gases in the space between thevaporizing and condensing surfaces and condensate on the vanes arecaused to pass to the side of the condensing surface farthest from thevaporizing surface, an evacuatwith that side of said condensing surfaceto which the gases are caused to pass, and means for removing condensatefrom the still.

10. An evacuating high vacuum still comprising in combination arotatable vaporizing surface, means for heating the vaporizing surface,means for introducing distilland onto the approximate center of thevaporizing surface, means for removing undistilled residue from thevaporizing surface, a rotatable condensing surface separated from thevaporizing surface by substantially unobstructed space, said condensingsurface being provided with vanes and slots therebetween, said vanesbeing so positioned, that during rotation distilling vapors impinge uponthat side of the vanes opposite from the vaporizing surface and so thatthere is ample space for passage of residual gases through the slots, anevacuating port the condensing surface opposite from the vaporizingsurface, and means for removing condensate from the still. KENNETH C. D.HICKMAN.

